Stand-by fuel feed control with hydraulic switching



Nov. 11, I952 .J. ISREELI ,6 7,477

STAND-BY FUEL FEED CONTROL WITH HYDRAULIC swrrcumc;

Filed Aug. 5, 1948 F054 RETURN 16 1 4-6 Maw CONTROL PUMP Hum

Tofiazz/e Galley 46 FIG. 2

H 60 A 51$ 7 5a 48 94 92 T A VINVENTOB Jack [sree/z 8.9/

Patented Nov. 11, 1952 STAND-BY FUEL FEED CONTROL WITH HYDRAULIC SWITCHING Jack Isrceli, New York, N. Y., assignor to Simmonds Aerocessories Inc., Tarrytown, N. Y., a

corporation of New York Application August 5, 1948, Serial No. 42,645

13 Claims.

1 My invention relates to improvements in jet engine stand-by control systems for thesupply of fuel to the engine in the event of the failure of the main control or fuel supply system. In a more particular sense my invention relates to improved automatic means for shifting the fuel supply to an engine from the main control to the stand-by control and the reverse.

Jet engines for aircraft are normally provided with a main automatic control and metering system for the supply of fuel to the engine in accordance with a given speed selection or schedule. An auxiliary stand-by control for the supply of fuel is highly desirable in engines of this type, particularly when they are used for military purposes, since either the electrical system or the main automatic control may be put out of order, damaged or shot away entirely.

In general, my invention constitutes an improvement upon a combined main automatic control and a stand-by control for jet engines of the type including a pipe-line for supplying fuel from a fuel supply and for delivering the fuel to the nozzle gallery and the jet engine, said pipeline leading through and being under control of the main automatic fuel control and metering system thereof, a separate fuel supply line for supplying fuel from a source to the stand-by control system and connected into the line from and beyond the main automatic control leading to the engine nozzle gallery, a fuel return line connected into each of said fuel supply lines, a valve in each of the connections to the return line for controlling the flow of fuel from the supply line to the return line, a check valve in each fuel supply line between said valves and the engine. nozzle gallery, pilot valve means for normally maintaining the valve between the main fuel supply line and the return line in closed position and an electrically controlled pilot valve means responsive to a predetermined pressure drop in the main fuel supply line between the main automatic control and the check valve in the line for closing the control valve between the stand-by fuel supply line and. the fuel return line.

A system of this type which includes a metering mechanism in the stand-by control line is disclosed in pending application Serial No. 42,464, filed August 4, 1948, of which I am one of the inventors. The present application and application' Ser. No. 42,464 are assigned to the same assignee.

, The primary object of my present invention is to provide an improved automatic change-over system for jet engines to automatically supply fuel to the engine through a stand-by fuel supply system in the event of a failure of the main control and the fuel supply associated therewith.

I have discovered that by providing a certain simplified arrangement in the system the fuel supply and the control thereof may be automatically changed over from the main automatic control to the stand-by control sysbem in the event of the failure of the main automatic control Or of the electrical system advantageously associated with the fuel supply systems. An important feature of my invention therefore is the provision of a hydraulic change-over system including an orifice in the main fuel supply line between the valve of the return fuel line and the check valve to provide a pressure differential in the line, and a pilot valve for the control valve between the stand-by fuel line and the return line having a diaphragm responsive to the pressure differential created in the main fuel supply line.

My improved change-over system also includes the feature of providing a needle type pilot valve operable by the diaphragm and having associated therewith a solenoid for operating the pilot valve, which in turn controls a supply of fuel for operating the control valve between the stand-by fuel line and the fuel return line.

An advantageous construction also includes a needle type pilot valve for controlling a supply of fuel for in turn controlling the positioning of the control valve between the main fuel supply line and the fuel return line, and a cut-off valve in the fuel line between these valves normally maintained in open position by a solenoid and by fuel pressure and which closes in the event of failure of the electrical system and a predetermined drop in pressure in the main fuel line.

In this application I illustrate and describe in detail one structural form embodying the features of my invention in connection with the accompanying drawings, it being understood that other structural forms may be made.

In the drawings:

Fig. 1 is a broken diagrammatic sectional view of an apparatus in connection With which the features of the invention are illustrated and described.

Fig. 2 is a broken diagrammatic sectional view of a portion of the apparatus shown in Fig. 1, illustrating a modified form of control for the pilot operated valve between the main fuel supply line and the fuel return line.

Referring to Fig. 1 of the drawings, the jet engine fuel supply is normally drawn from a supply tank, not shown, through a supply line id, and forced by an engine driven pump 12 through a line 14 into a main fuel metering and control system of known design and construction and shown diagrammatically at It. The fuel metered through the control system it under normally operating conditions, is delivered through a line I8 having a check valve 20, into a main fuel line 22 leading to th nozzle gallery of the jet engine or engines.

In order to increase the safety of the aircraft and insure operation of the jet engine in case of emergency, the fuel for te stand-by control is not taken from the pump l2 or the supply line It, but is drawn from a fuel tank, not shown, by a pump 24 which is advantageously independently driven by an electric motor, not shown.

the main line 22 leading to thenozzle gallery of The link 36 is alsoconnected by a link '40 anda lever 42 with the metering device of the standby automatic coritrol 28.

In the normal operation of the apparatus, fuel is supplied continuously by pumps l2 and 24, and even when the main control is malfunctioning there may be some fuel supplied into the line [8. Provision is made for bypassing fuel either from theline IE or thejline 26Ito a fuel returnoline44. This means includes a branch. line '46 .between the line l8 and the return line 44, immediately down stream from the control [6, the line 46 being provided with a spring biased valve 48. In a similar manner, the line 25,, in advanceof the stand-by control 28, is connectedIby. a fuel line 55 with the fuel return linej'4f4, the line 55 being provided with a spring biased valve 52. The

valves or valve members 48 and'52 are' constructed alike and operated in substantially the same mannenthat is, by the'pressure of fuel in front and in back of these members. 7

Theapparatus shown in Fig. l is illustrated with the vaives'ahd associated means in a positiont'ofsupply fuel through t'h e stand -by control, as'rnay. b e the case in theengine starting position, the valve 48 being openand the valve 52 being closed, so that fuel is bypassed from the line is to the line 44,while the engine is supplied with fuelfromothe line 26 through the stand-by metering controlZB and thecheck valve 32. The check valves 23 and 3 2 are provided with light springs so as to provide minimum flow restriction. As shown, the check valve 20 is held closed by the pressure 'ofrfuel supplied through the stand-by control system.

The valve 48 controls a relativelylarge open-o ing, and it is therefore advantageously operated by a needle type pilotvalveg 4which is arranged to be closed by a solenoid 55. The valve 48 is shown as being held open against a spring by the pressure offuel in the, line l8. This valve is closed when the, solenoid56. is de-energized and the needle valve 54. permitted to open, so that'fuel will flow through thevalve 54 anda passageway 53 into the space in back of the valve48, this space being vented to the return line 46 by a pas- 'line [8.

sageway provided with an orifice 60. The at rangement is such that the pressure of liquid flowing through the valve 54 and passageway 58 in back of the valve 48 holds it against its seat while a small amount of fuel continuously flows through the orifice 68. Since the pressure of fuel on each side of the valve 48 is equalized, the valve will be held to its seat because its back area is greater than the area of the front of the valve projecting through its seat and facing into the When the solenoid 56 is energized, as shown in Fig. l, the valve 54 is closed, and therefore the pressure in back of the valve 48 falls ofi because of leakage through the orifice 60, so that the pressure in the line 18 moves the valve to open position.

The valve' 52- is actuated in the same manner as the valve 48 but a needle valve 62 associated therewith has other functions. When the needle valve 62 isopened a 'shown, fuel from the line 2 6 flows through a passageway B 4 in back of the valve 52 and is bled slowly through an orif ce 615. The fuel pressure in back of the valve 52.,keeps it seated because of the different valve areasreferred to 'aboveiin connection'with th'e valv 48.

.The stem 68 of the needle valve 62; is actuated by a solenoid 70 when itis desired to close the valve by the electrical system. Means fis provided for causing the valve "62 to snap frorn open to closed position comprising'a recess in the stem of the valve 62 engagingthe spring catch 'l2 when the valve 6 2 is open. The snapaction isobtained because of the initial resistance providedby'the catch 12 when pressure is applied to closethe valve 62. A diaphragm 14 is attached tothe stem 68 and arranged to'provide a pair of annular chambers 15 and 15 around the stem for receiving fuel from the line 1 3, The dia hragm 14 is acted upon by a light. spring 11 which tends to keep thevalve 62 open. The chamber 1 6 tothe right'of the diaphragm is connected by apassageWay 'Hi into the I fuel; line l a t p-stream from a flow restricting orifice 8 0, while the chamber on h p o e h aph a m l connected by a passageway'82 with the fuelline lBdownstream from'the' orifice 80.

e 7 Under normaljop eratingconditions, the'valve 5 4 is open, the. valve 43; closed, the valve 62 closed, and the valve 52 open. The pressure dropac rossthe orificeSO is norm'ally sumcie'ntto carry the needle valve 62 and the solenoid plunger or stem 68fto the left, so that'the valve 62is closed and maintained closed. Now, if for some reason, the maincontrol l6, or'fuel supplied thereto, should fail, the pressure. drop across the orifice wouldg be'reduced tosuch an extent as pump 24, the mainautomatic control 16; should berepaired or go back 'intoxnormalsoperation, fuel would; flow, through :the valve 54. and "passageway 58. to'close the valve-48:, thereby creatingthe normal pressure drop across the orifice 80, which would act upon the diaphragm 14 to closethe valve.62 an'd therefore openthe valve 52. At the same, time, the fuel pressure in the li'n'e1'8- wo'uld open the check valve and close the check valve 32.

The electrical system for the solenoids 56 and 19 includes any suitable source of electricity; such as a battery 84, one terminal of which is grounded, a switch 86 and a wire 81, for energizing the solenoid 18, one side of which is grounded. The electrical system also includes a switch 88 connected by a wire 89 to the solenoid 58, one side of which is grounded. The pilot may operate the switches 86 and 88 from buttons 98 and 9|.

When the electrical system is in operation, as illustrated in Fig. 1, it is apparent that the pilot may select the stand-by control or the main control at will. If both switches 86 and 88 are left open, the main control will function, and if anything should happen to the metering system I5, the pump I2 or the fuel supply, the stand-by control system would automatically cut in, in the manner explained above. However, if the operator wishes to select the stand-by control, for example, in starting the engine, since the pump 24 is electrically driven and the pump 12 is driven by the engine, he actuates the switch button 9! to close the valve 54 and thereby bypass the fuel from the line [8 through line 46. Since the valve 62 is open, the valve 52 will be closed and fuel will be supplied through the stand-by control. After the engine is in operation the pilot may switch over to the main control by opening the switch 88 and closing the switch 86. When the electrical system is in operation, the valve 82 may be held closed by solenoid 10. If the electrical control system should fail, and the main fuel supply system is still in operation, the valve 82 will be held closed by the pressure of fuel on the diaphragm 14. The switch buttons 90 and 91 may be used as a cut-off for the engine since when both switches are closed the solenoids 55 and H1 will be energized to close the valves 54 and 82, so that valves 48 and 52 will open and the check valves 29 and 32 will close to stop the supply of fuel to the engine.

The stand-by control system is scheduled to meter a quantity of fuel slightly less than that supplied by the main control, the latter being regulated by the lever 38 while the stand-by metering control is regulated by the lever 42. Under these conditions, it is possible that after the main control has failed that it could produce short-lived pressures of a higher value than that of the rated pressure of the stand-by control, and therefore cause a change from the main system to the stand-by system and back again, under conditions which might give unsatisfactory engine operation. A change-over from the main supply to the reserve supply and back again can occur when the operator desires to check the reserve supply system for proper operation prior to take-off, or the change-over sequence can occur in flight if the main supply fails momentarily due possibly to temporary icing or dirt clogging. As long as the electrical control system is in operation this changing back and forth can be avoided by closing the switch 88 to keep the valve 54 closed and the valve 48 open.

However, the apparatus as shown in Fig. 1, may advantageously include a cut-off valve 92 such as shown in Fig. 2 which comes into operation in case of the failure of the main control or of the electrical control system. It will be noted that the valve 92 is arranged to close the passageway 58, and that it is held open against the biasing springby energizing asolenoid 94.

If the electrical control system should fail and the main control is operating to supply fuel through the line I8 at normal pressure, the valve 92 is kept open against the valve spring by the fuel pressure in the passageway 58. As soon as the main fuel supply system fails so that the pressure therein falls below the established minimum, the spring for the valve 92 moves the valve to close off the flow of fuel through the passageway 58, thereby permitting the opening of the valve 48. At the same time the valve 62 would be opened and the valve 52 closed to send fuel through the stand-by system. The solenoid 94 is supplied with current through a line 96 which may be connected up through a switch in the pilots cockpit and arranged'to take current from the battery 84 or other suitable source.

From the foregoing description, it will be apparent that the improved apparatus of the present invention provides a system which is automatic and effective for the changing over of an engine fuel supply from a main control and supply system to a stand-by fuel supply and control system. The particular elements of the apparatus, and to some extent their arrangement, may be changed without departing from the spirit and scope of the invention as defined by the appended claims.

What I claim is:

1. In an apparatus for controlling the supply of fuel to an engine, means including a main fuel line for conducting fuel from a fuel supply to the engine, a main automatic fuel supply control in said line, a stand-by fuel supply line separate from the main fuel line for conducting fuel from a fuel supply to the engine, a stand-by fuel supply control in the stand-by fuel line, a fuel return line connected into the main fuel line down-stream of the control therefor and having a control valve therein, a fuel return line connected into the stand-by fuel line up-stream of the control therefor and having a control valve therein, means for normally maintaining the control valve in the fuel return line from the main fuel line in closed position, a check valve in the main fuel line down-stream of the fuel return line therefor, a flow-restricting means in the main fuel line between the check valve and the fuel return line therefor for creating a normal pressure drop in the main fuel line at the position of said flow-restricting means, and means responsive to the maintenance of a normal pressure difference in the main fuel line on opposite sides of said flow-restricting means for keeping the control valve open in the fuel return line from the stand-by fuel line.

2. An apparatus as defined by claim 1 in which the control valve in the fuel return line from the stand-by fuel line includes a piston-like valve member mounted in a cylindrical chamber, a passageway for fuel from the stand-by fuel supply line to the back portion of the chamber in which the piston-like member moves, a passageway having an orifice therein leading from said chamber to the return line from the stand-by fuel line, and a needle-valve means in said passageway for fuel from the stand-by fuel supply line, said needle valve means being responsive to fuel pressure changes in the main fuel line for controlling the flow of fuel through said passageway from the stand-by fuel supply line.

3. An apparatus for controlling the supply of fuel to an engine as defined by claim 1 in which the control valve in the fuel return line from the stand-by fuel supply line includes a piston-like.

chamber, a passageway leading fromthestandw byfuel supply line tothechamberinback ofthe piston-like member a .passagewayhaving a leake age orifice leading ,fromsaidchamber, into the fuel return line from.the.stand,- -by fuel line a small ,valve in the passageway leading fromthe stand-by fuel supply line, asolenoidioperatively associated with said small valve, for effectingits operation, and means. responsive to pressure changes in themain-.fuel linev for operating said small. valve.

4. .An apparatus for; controlling; the: supply. of fuel to an engine as. defined in claim 1, characterized by including. a valve member, for each icon-. trol valve,.and. a-relatively small pilotvalve for controlling the actuation ,of each .valve -.member, thereby controlling the flow of fuel to the return 1ine,,the pilotvalve for the control valve. in the stand-by return line beingconnected to. said re-. sponsive. means, and operable thereby.

5., An apparatusas defined by claim Lin which the control valve. for controllingthefiow offuel from the stand-by fuelline into, its. returnline includes a piston-like valvememberlmoun-ted in a cylindrical chamber, a passageway for. fuel from the stand-by fuel supply line'to oneende portion of the chamber in which ,the=-piston-like member. moves, a needle-type valve. member-in said passageway for controlling, the flow of fuel therein, said needle-type valve having a stem ex.- tending through achamber and attached to a diaphragm dividing the chamber in two, and passageways respectively connecting the chama bers on theopposite sides of said diaphragm with themainfuel supplyline, one above and jone ,below. said flow-restricting means.

6. An apparatus as defined by-claim 5'in which the ,chamberonthe side of said diaphragm opposite the needle-type valveis connected intothe main fuel supply line upstreamfromsaid'fiowrestricting means, whereby the pressure drop created'in the main fuel supply line is effective for maintaining said needle-typevalve.injclosed position.

7; An apparatus as defined by claim 6 in which the stem of the needle-type valvecomprises the plunger of'a solenoid for actuating the needle.- type valve to closed position.

8. An apparatus as defined by claim 1 in'which the control valve in the fuel return line from the" main fuel supply line comprises a hydraulically operated piston-like valve member movable endwise in a chamber, a passageway between-the, main fuel line and a chamber'inback ofsaid piston-like member, a valve in said passageway including a piston-like member normally retainable in open position by the pressureiof fuel in the passageway, and a solenoid adapted-to-hold said last-mentioned Valve member in open posi'-" tion when energized.

9. An apparatus as defined by claim 1 in which the control valve in the fuel return line from the main fuel supply line includes a piston-like mem.

ber movable endwise in a chamber, a passageway for fuel between the main fuelline and the chamber in back of the piston-like member, a. solenoid operated needle-type valve for said passageway, a second valve for said passageway including a piston-like member normally retainable in open position by the pressurelof fuelin said passageway, and a solenoidfassociatedjwith the. piston-like valve memberoflsaidjpassagee 10. A change-over system for the supplyof liquid including a common outlet line, a=main supply line for. conducting liquid to said outlet line, a stand-by supply line for. conducting liquid to said outlet line, a returnli-ne connected into each of said supply lines, a--.control*va1ve in each connection to the returnline, the control valve inthe connection between-the stand-by line-and the return-line being a. hydraulically operated valve comprising apiston-like closure member mounted for reciprocation in a chamber, a-floW-restricting means in the main supply line down-stream of itsconnection to the returnline for-creatingapressure dropyinthe main supply line, a hydraulically-operated means responsive to the maintenance of a pressure'drop in the,

main supply lineat the positionof said flow-restricting means for keeping the piston-likevalve member in openposition for the'fiow ofliquid from the stand-bysupplyline to the return line,

said hydraulically-operated means including a passageway'from the stand-by supply; line to the chamber in backofthe piston-like valve member, a .needletype valve member for-said-passageway,,means forming apair of chambersadjacent saids-needle-type valve member including a flexible diaphragm separatingsaid chambers, said-needle-typevalve member having a stem extending through one of saidrchambers and attached -tosaid. diaphragm foroperation thereby,

a biasing spring around the stem and arrangedv to urgethe diaphragm in a. direction to movethe low pressure. side --ofsaid flow-restricting.

meansto thechamber'onthe side of said-diaphragm; adjacent the needle-like valve. member.

12. A changeeover systemwfor... theLsupplypf liquid including a common..outlet line a main supply line for conductingliquid-tosaid outlet line, a .stand-bysupply .line for conducting" liq? uid tosaid outlet-line, a return line connectedinto .each of .said supply lines a control 'valvein. each. connection. ,to the; return line, the control valve. in the connection between .the' stand-by lineiand the return line being a hydraulicallyposition.

operated .valve comprising a piston-like closure member mounted for'reciprocationin a. chamber,

aflowrrestricting'means in the main supply-line down-stream of its connection to the return. line forcreating a pressuredrop in the. main supply line; a hydraulically-operated Imeans responsive to. the maintenanceof .,a pressure drop in the main. supply line at the positionof said fiowrestricting means for keeping the piston-like valve member in open *position for theifiow'of liquid from the stand-by supply line 'to thereturn line,

said hydraulically-operated'means including a' supply line for conductingliquid to "said outlet' line, va'stand-by supply line for conductingliquid to said outlet line, a return line connected 'into each of said supply lines, a control valve in each connection to the return line, the control valve in the connection between the stand-by line and the return line being a hydraulically-operated valve comprising a piston-like closure member mounted for reciprocation in a chamber, a flowrestricting means in the main supply line downstream of its connection to the return line for creating a pressure drop in the main supply line, a hydraulically-operated means responsive to the maintenance of a pressure drop in the main supply line at the position of said flow-restricting means for keeping the piston-like valve member in open position for the flow of liquid from the stand-by supply line to the return line, said hydraulically-operated means including a passageway from the stand-by fuel supply line to the chamber in back of the piston-like valve member, an orifice bleed from said chamber, a snapacting needle-type valve for controlling the flow of liquid in said passageway, and means for normally holding said needle-type valve in closed 10 position thereby permitting said piston-like valve member to be in open position for the flow of liquid from the stand-by supply line to the return line.

JACK ISREELI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,229,132 Samiran Jan. 21, 1941 2,394,506 Woods Feb. 5, 1946 2,431,345 Samiran Nov. 25, 1947 2,440,262 Groy et al. Apr. 27, 1948 2,440,371 Holley Apr. 27, 1948 2,464,802 Davin Mar. 22, 1949 FOREIGN PATENTS Number Country Date 918,123 France Oct. 7, 1946 

